Which Diode(s) Should I Use ?

[ToddB74]

ToddB74,
I can understand the concerns about you safety by people replying to your post. In your first post you label an AC supply with + and -. You have no earth connections and you use an internet calculator for a simple thing like calculating the value of the series resistor for an LED. When someone mentions the use of + and - you say it is to indicate polarity. The polarity of an AC supply reverses every 8.3 mS (Assuming a 60 HZ supply.)

Les.

Hi Les !

Thanks for your critique !

In my circuit sketch, I should have labeled the + and - as L and N (Live and Neutral).

Misterbenn has got me going now if you want to view his post #18 and my reply, post #19.

Happy trails !
ToddB74

 

[ToddB74]

Just a note on your test setup. Breadboard is not designed for hv and i suspect will have corona if not actual arcing.

I suggest using veroboard for the proto with some copper tracks scrapped off.

Also make sure to use a fuse, but I'm sure you know that.

Misterbenn.......Thanks again for keeping me on track.

I have an Archer catalog no. 276-170 Experimenter Printed Circuit Board, with copper tracks for the proto.

Yes, I will fuse my Portable Outlet Box, but I assume you are talking about just a small fuse to protect the Marc's bridge rectifier circuit . Considering the Mains breakers protecting any one of the 15 A wall outlets I might choose to power my portable outlet box, wouldn't a small fuse for the bridge rectifier be all that's really necessary ?

ToddB74

 

[audioguru]

Yes, I almost asked you to post the video of your breadboard catching on fire.

 

[Misterbenn]

Yes, I will fuse my Portable Outlet Box, but I assume you are talking about just a small fuse to protect the Marc's bridge rectifier circuit . Considering the Mains breakers protecting any one of the 15 A wall outlets I might choose to power my portable outlet box, wouldn't a small fuse for the bridge rectifier be all that's really necessary ?

Yes that's all that is needed in the final product.

But personally for the prototype I'd use as a minimum in terms of protection a fused supply using a <1A quick blow fuse. I know you probably have residual current protection in the distribution panel for the outlet but that wont help if you have a line to line fault. And although you have a 15A breaker you should be aware that

1. 15A is the continuous current, for a short duration much higher currents can flow
2. 15A is plenty enough to kill you
3. the copper traces on your proto board wont be good for 15A, so in the event of a short these may catch fire / explode / melt
4. an arc flash even at just 15A is very dangerous and can cause serious harm.

With the above in mind I'd perform all testing of the proto in a closable and clean plastic enclosure. This removes many of the risks associate with accidental shorts, electrocution and exploding copper!

 

[ToddB74]

voltage regulator

Yes that's all that is needed in the final product.

But personally for the prototype I'd use as a minimum in terms of protection a fused supply using a <1A quick blow fuse. I know you probably have residual current protection in the distribution panel for the outlet but that wont help if you have a line to line fault. And although you have a 15A breaker you should be aware that

1. 15A is the continuous current, for a short duration much higher currents can flow
2. 15A is plenty enough to kill you
3. the copper traces on your proto board wont be good for 15A, so in the event of a short these may catch fire / explode / melt
4. an arc flash even at just 15A is very dangerous and can cause serious harm.

With the above in mind I'd perform all testing of the proto in a closable and clean plastic enclosure. This removes many of the risks associate with accidental shorts, electrocution and exploding copper!

Misterbenn,

Thanks for this additional information and advice !

You have been and are of great help to me.

At the present time, while I have interest in electronics overall, I'm fascinated in particular with LEDs, adding single LEDs to various devices and most important, acquiring the head knowledge to correctly choose and arrange appropriate components (led, voltage regulator, resistor, diode, capacitor, etc.) for different applications. As time goes by, I might gain interest in multi-Led applications, but for now, single led applications are enough for me. Be assured, until I work with complexities enough to rely on my memory, I always keep copious notes and/or copies of documents on everything, as reminders......assume any serious student does the same.

ToddB74

 

[Tony Stewart]

This what I intended < simulatorhttps://www.falstad.com/circuit/cir...5+2+-1 o+13+64+1+35+0.625+0.00009765625+2+-1

Top circuit
Simple but generates 100x more heat.than the LEDs due to voltage ratio.
Each LED goes on 1 at a time for each half cycle. ( slight flicker)
Need 2 diodes to protect from reverse V damage
36mW peak is around 15mW avg or ~25% of rated 5mm LED power

Bottom circuit
< 1/2W of heat due to series cap. reactive high impedance ~10kΩ
But Cap causes impulse worst case if switched on at Vac peak of 25W in series 1k2 Res., so WW type is recommended
Cap must be film line rated usually PE or PU X1 type. ~$1
Power can be reduced further using an UltraBright >5000~10k mcd LED for just an indicator to 10% of rated 60~65mW.

 

[ToddB74]

Tony,

Your post #26 is very interesting !

I've been reading about the advantages of Ultra-Bright LEDs.

And what are your thoughts on substituting an LM317T adjustable voltage regulator on a
one-LED application (such as mine at the moment), instead of using resistors ?

Thanks for your help.

ToddB74

 

[Les Jones]

Hi ToddB74,
You seem to want to make this indicator light as complicated as possible. If you look at the absolute maximum rating for the LM317T you will see that the maximum input/output differential is 40 volts. So to use this you first need to drop the voltage down to less than 41.8 volts DC (assuming a 1.8 volts LED) To do this you would need the capacitor (Slightly different value.) and resistor of Tony's second circuit followed by a bridge rectifier and smoothing capacitor to provide the DC input to the LM317T This would be a very bad design as using the reactance of the capacitor to drop the voltage provides more of a constant current source than a constant voltage source. The input voltage to the LM317T would be defined mostly by the current output of the LM317T (This would apply weather you configured LM317T either as a constant current regulator or as a constant voltage regulator with a resistor on the output to set the LED current.) You could get round this problem by adding a 40 volt zener diode in parallel with the smoothing capacitor. A further reason that using the LM317T to drop the voltage by 40 volts is it would generate extra heat (40V x 20 mA = 800 mW)

Les.

 

[ToddB74]

Hi ToddB74,
You seem to want to make this indicator light as complicated as possible. If you look at the absolute maximum rating for the LM317T you will see that the maximum input/output differential is 40 volts. So to use this you first need to drop the voltage down to less than 41.8 volts DC (assuming a 1.8 volts LED) To do this you would need the capacitor (Slightly different value.) and resistor of Tony's second circuit followed by a bridge rectifier and smoothing capacitor to provide the DC input to the LM317T This would be a very bad design as using the reactance of the capacitor to drop the voltage provides more of a constant current source than a constant voltage source. The input voltage to the LM317T would be defined mostly by the current output of the LM317T (This would apply weather you configured LM317T either as a constant current regulator or as a constant voltage regulator with a resistor on the output to set the LED current.) You could get round this problem by adding a 40 volt zener diode in parallel with the smoothing capacitor. A further reason that using the LM317T to drop the voltage by 40 volts is it would generate extra heat (40V x 20 mA = 800 mW)

Les.[/QUOTE

Les.......Thanks for straightening me out on that ! I got the idea from reading a document on LEDs, titled Problems Using Resistors to Regulate Current at the following website > http://www.reuk.co.uk ( Click-on this article > Using The LM317T With LED Lighting - Lighting )

So I'll forget about using the LM317T voltage regulator on my current application.

I appreciate you're taking the time to explain.

ToddB74

 

[audioguru]

I've been reading about the advantages of Ultra-Bright LEDs.

Warning. Did you read that many "Ultra-Bright LEDs" sold on ebay are simply an old dim LED in a case that focuses its light into a bright but very narrow beam? They can barely be seen if they are not shining directly at you. A modern bright LED shines all around.

 

[Tony Stewart]

LEDs have improved over 1000x brightness in the last 3 decades, so using less current is required 1-2 mA min.

Dropping voltage to 1% from 120V rms to Vf means 100x voltage drop in series.
Using 3W resistor is easiest using 3mW of 65mW LED if using ultrabright type.

Iv measured in mcd or Cd almost doubles for 1/2 of the beam focus minus lens loss of 10% per octave. So from 60 to 30 to 15 is almost 4x -20%

 

[ToddB74]

Its exactly because you are a newbie that everyone is suggesting neon lamps.

Don't get me wrong I encourage learning, but this is a potentially dangerous project to start off on. Unless you use a isolation transformer (and I suspect you wont due to complexity and size) you are talking about a mains connected circuit without a proper understanding of electrical safety and component failure modes. You could hurt yourself on this endeavor, but to be honest that's not what I'm concerned about. If you hurt yourself well that's your own fault but the set up you suggest could be used by a layman (general person) and hurt them and that's far more concerning.

If you want to learn I suggest getting a 230V to 12 or 24Vac step down transformer and fast blow low current <<1A output fuse. This will let you create practice circuits and develop understanding while not endangering yourself or anyone else.

If you want a quick solution which is quick and for the most part safe (not completely because the neon could have exposed wires if your enclosure isn't very good or not grounded correctly), then just buy a neon.

Again i just want to say i encourage learning and if you're proceeding safely I'm sure we'll all be happy to help guide you. But main's voltage is not something a "electronics newbie" should be playing with and its certainly not suitable for just lifting a circuit off a forum without deep understanding of what you are doing.

Hi Misterbenn !

Would you expect all portable multi-outlet blocks like the one shown in the photo below, most of which appear to use LEDs, have an isolation transformer inside or a small electronic device that performs the same function ? If so, do you know of a small device of that type for circuits where space is limited that I could use inside a plastic test box with lid (to protect against exploding components and fire.) and inside my final Portable Outlet Box ?

BTW, I've been reading electronics posts and pdf tutorials on the Internet and noticed others also advising to include an isolation transformer when using AC to power an LED through a sub-circuit that includes a resister, capacitor, bridge rectifier and fuse.

Thanks again !

ToddB74

 

[Les Jones]

Hi ToddB74,
The outlet strip shown in your post #32 will use a neon not an LED. Manufacturers use the most cost effective solution they do not add complexity just just on a whim.

Les.

 

[Misterbenn]

Would you expect all portable multi-outlet blocks like the one shown in the photo below, most of which have one or more LEDs, have an isolation transformer inside or a small electronic device that performs the same function ? If so, do you know of a small device of that type for circuits where space is limited that I could use inside a plastic test box with lid (to protect against exploding components and fire.) and inside my final Portable Outlet Box ?

I wouldn't imagine any multi-outlet blocks have isolation transformers or LEDs for the same reasons that Les Jones states.

However shaver sockets use isolation transformers for protection and this is probably the most common example of there use. Also the construction industry uses larger isolation step-down transformers to reduce the voltage to 115V (less risk of electrocution and arc flash) you can find some here https://uk.rs-online.com/web/c/power-supplies-transformers/transformers/safety-site-transformers/ .

For isolation you would need to find a 1:1 transformer rated for the power level and voltage you need, but for prototype its probably just easier to wire up a shaver socket and plug in your test box. Just check the power level is suitable.

 

[Tony Stewart]

This powerstrip probably just has a 10 cent MOV and a pushbutton breaker on end and a power switch with builtin neon indicator & >=100kΩ current limit for the tube.

This is about all you can expect.

Isolation transformers are massive at 50/60Hz

Does it have a legit UL registration #?

 

[ToddB74]

Hi ToddB74,
The outlet strip shown in your post #32 will use a neon not an LED. Manufacturers use the most cost effective solution they do not add complexity just just on a whim.

Les.

Thanks for correcting me Les ! Looking at the outlet block in my room, it's hard to tell from appearance alone whether the lights are neon or led. From the size I just assumed led.

ToddB74

 

[ToddB74]

I wouldn't imagine any multi-outlet blocks have isolation transformers or LEDs for the same reasons that Les Jones states.

However shaver sockets use isolation transformers for protection and this is probably the most common example of there use. Also the construction industry uses larger isolation step-down transformers to reduce the voltage to 115V (less risk of electrocution and arc flash) you can find some here https://uk.rs-online.com/web/c/power-supplies-transformers/transformers/safety-site-transformers/ .

For isolation you would need to find a 1:1 transformer rated for the power level and voltage you need, but for prototype its probably just easier to wire up a shaver socket and plug in your test box. Just check the power level is suitable.

Thanks Misterbenn ! I will look at a shaver socket and may come back with a question(s).

ToddB74

 

[ToddB74]

This powerstrip probably just has a 10 cent MOV and a pushbutton breaker on end and a power switch with builtin neon indicator & >=100kΩ current limit for the tube.

This is about all you can expect.

Isolation transformers are massive at 50/60Hz

Does it have a legit UL registration #?

Thanks for the information Tony !

Re your question "Does it have a legit UL registration #?", the outlet block in the photo attached to my post #32 isn't mine; it was just a photo I copied & pasted to go along with my post for viewer reference only.

ToddB74

 

[Tony Stewart]

The other interesting and useless bit of information about neon tube indicators is they are negative resistance devices like DIAC's but at a higher voltage and only one lead glows when used on DC.

 

[ToddB74]

The other interesting and useless bit of information about neon tube indicators is they are negative resistance devices like DIAC's but at a higher voltage and only one lead glows when used on DC.

Hummm ...... Maybe "useless" as you say Tony, but nevertheless interesting to me !

Thanks for the info. !

ToddB74